Known in the art is a method for preparing phthalonitriles by oxidative ammonolysis of xylene in the presence of a catalyst consisting of a mixture of vanadium oxide and molybdenum oxide deposited onto alumina activated by compounds containing cerium, manganese, tin, bismuth, antimony, titanium, lithium, sodium and potassium (in an amount of from 0.1 to 50% by the total weight of vanadium and molybdenum). Upon passing through the catalyst a mixture containing 0.77% by weight of p-xylene, 7.22% by weight of ammonia and 92.05% by weight of air during the contact time of 0.77 sec, at the temperature of 460.degree. C., the maximum yield of terephthalontrile is equal to 95.4% by weight, that of isophthalonitrile is 85% by weight, the yield of ortho-phthalonitrile is 80% by weight as calculated for the employed xylene. Under these conditions the catalyst capacity relative to terephthalonitrile is 72.4 g/l of the catalyst per hour; the catalyst capacity relative to isophthalonitrile is 60 g/l of the catalyst per hour (cf. U.S. Pat. No. 3,870,743).
Also known in the art is a method for preparing terephthalonitrile by way of oxidative ammonolysis of p-xylene with recycle of the unreacted starting hydrocarbon and intermediate nitriles in the presence of a catalyst consisting of 1.3% by weight of V.sub.2 O.sub.5 and 8.1% by weight of Sb.sub.2 O.sub.3 deposited onto alumina. At the temperature of 454.degree. C., space rate of 1,100 hr.sup.-1 conversion of p-xylene per pass is 50%, selectivity relative to terephthalonitrile is 33 mol.%. The catalyst capacity relative to terephthalonitrile under these conditions is equal to 62 g/l of the catalyst per hour (cf. U.S. Pat. No. 3,497,545).
Another method stipulating the use of the same catalyst (1.3% by weight of V.sub.2 O.sub.5 and 8.1% by weight of Sb.sub.2 O.sub.3) and contracting thereof with p-xylene, ammonia and steam (1.5:82.5:6.0:10% by volume) makes it possible to produce terephthalonitrile with the selectivity about 80 mol.% at the 100% conversion of p-xylene (cf. U.S. Pat. No. 3,393,220).
French investigators have studied the reaction of oxidative ammonolysis of p-xylene in the presence of V.sub.2 O.sub.5, V-Mo, Ti-Mo and Sn-Mo catalysts. The maximum yield of terephthalonitrile of 79% by weight is reached when V.sub.2 O.sub.5 is used as the catalyst. The process temperature is maintained within the range of from 415.degree. to 460.degree. C., molar ratio of p-xylene:ammonia:air is equal to 1:10:100 (cf. Bull. Soc. Chim. France, 1975, Nos. 11-12, pp. 2617-2621).
Known is a method for preparing terephthalonitrile by way of oxidative ammonolysis of p-xylene or diethylbenzene in a stationary or fluidized bed of a catalyst consisting of oxides of vanadium, chromium, boron, phosphorus (atomic ratio between the elements being equal to 1:(0.5-2):(0.1-1.2):(0.01-0.3)) deposited onto silica gel. Passing a mixture consisting of 1.2% by volume of p-xylene, 9.6% by volume of ammonia and 80.2% by volume of air over this catalyst at the temperature of 305.degree. C. over the contact time of 6 sec results in the content of terephthalonitrile in the reaction products equal to 85.2 mol.%. Capacity of the catalyst relative to terephthalonitrile is equal to 14 g/l of the catalyst per hour.
Known in the art is a method for preparing terephthalonitrile by way of oxidative ammonolysis of p-xylene at the temperature of 360.degree. C. and the contact time of 6 sec in the presence of a catalyst, i.e. vanadium oxide supported on alumina. The yield of terephthalonitrile is 70% by weight (cf. British Pat. No. 796,765).
A principal disadvantage of the above-discussed methods resides in an insufficient yield of the desired product and a low capacity of the catalyst.
Also known in the art is a method for preparing phthalonitriles by way of oxidative ammonolysis of xylene. The process is conducted at a temperature within the range of from 340.degree. to 380.degree. C., the molar ratio between xylene, ammonia and air oxygen of 1:7:20, contact time of from 0.6 to 7 sec in the presence of a catalyst containing 21% by weight of antimony oxide, 3.2% by weight of bismuth oxide, 5% by weight of vanadium oxide or molybdenum oxide supported on alumina. Under these conditions selectivity of terephthalonitrile constitutes 93 mol.%, the catalyst capacity with respect to terephthalonitrile is equal to 67 g/l of the catalyst per hour, in respect of isophthalonitrile and orthophthalonitrile the catalyst capacity is equal to 57 g/l of the catalyst per hour.
This prior art method has a disadvantage residing in a low capacity of the catalyst and an insufficient yield of the desired product.